Detection of adulterated samples

ABSTRACT

In some embodiments, the present invention pertains to a method for detecting an adulterant in a biological sample. A combination of a biological sample, an agent for detecting the adulterant and an ionic moiety capable of undergoing reduction by gaining electrons is provided in an assay medium. The combination is incubated under conditions sufficient for the ionic moiety to undergo reduction and for the agent for detecting the adulterant to interact with the adulterant. The reduction of the ionic moiety enhances the detection of the adulterant as a result of increasing the sensitivity of the agent for detecting the adulterant. The extent of interaction between the agent for detecting the adulterant and the adulterant is measured and is related to the presence or absence of the adulterant in the biological sample.

BACKGROUND

This invention relates to the determination of drugs of abuse. In someembodiments the invention relates to enhancing detection of adulterantsthat may be present in a biological sample to be tested for drugs ofabuse.

As the use of illicit drugs has increased, public concern over theproblems associated with its effects has grown. Drug use is generallyrecognized as a significant contributory factor in the current rise ofaccidents. Employers, government organizations, and others areincreasingly using drug screening and freedom from drugs as conditionsof employment. This concern has led to workplace drug testing in orderto identify, treat, and remove active drug users from the workforce.Initial drug testing in the workplace revealed the obtrusive incursionof drug use and abuse in the daily lives of a significant portion ofAmericans. Further research indicated the staggering costs to public andprivate industry in terms of lost productivity, increased health carecosts, and human suffering and death due to drug abuse. As a result,drug testing has spread to all areas of the public and private sector.

Because of the above, individuals may be requested or required toprovide a sample such as a urine sample that will be tested for thepresence of drugs of abuse or metabolites of drugs of abuse. An initialor screening test is frequently performed first. A positive result isusually confirmed by a method different from that used for initialtesting, which usually has greater sensitivity and specificity than theinitial test. An initial negative test, however, is usually notconfirmed. Thus, an individual who is fearful of a positive result in aninitial screening test may alter his or her urine sample to preventdetection of the drug or drug metabolite.

Many screening tests utilize antibody-antigen reactions quantified bymeans of an enzyme indicator. The confirmation assays, on the otherhand, are labor and time intensive, highly accurate, expensive, and moredifficult to adulterate. In addition, the positive screen has alreadyraised a red flag, thereby drawing attention to the sample. Theconfirmation analysis utilizes GC-MS (gas chromatography massspectrometry) testing which is considered the “gold standard” for drugassays scientifically and legally.

One method of altering a urine sample is by diluting the sample so thatthe drug or drug metabolite concentration is below the detectionthreshold in a screening test. For example, water and/or saline may beadded to the sample to dilute the drug or its metabolite to aconcentration that is less readily detected by the screening test. Todetect this type of alteration, the urine sample is frequently assayedto determine if physiological parameters such as creatinineconcentration, pH, and specific gravity are within normal ranges, or ifthese parameters are abnormal due to the presence of diluent.

Chemical adulterants may be added to a sample in an attempt to produce afalse negative result in the initial screening test. In some instances,the chemical adulterants chemically convert a drug or a drug metaboliteto a less detectable or non-detectable product. Adulteration techniquescan be divided into two distinct types. The first utilizes an “in vivo”technique in which the user consumes the adulterant. The secondtechnique utilizes an “in vitro” method in which the abuser adds theadulterant directly to the urine specimen submitted for testing.

In vitro methods utilize numerous products and compounds that willadversely affect either the screening or confirmation process. Productsaffecting the screening process include many household products and alsocommercially available products sold for the purpose of obscuring theresult of a drug test. These products include oxidants such as, forexample, hydrogen peroxide, sodium nitrite, bromates such as, e.g.,sodium bromate, potassium bromate, etc., bromine, bleach (sodiumhypochlorite), chromates such as, e.g., pyridinium chlorochromate, etc.,nitrites, iodine, iodate, iodic acid, periodate, and the like.

The presence of chemical adulterants is more difficult to assess, sincetests for the specific chemicals must be performed. As each new chemicaladulterant is recognized and identified, tests are developed foridentification of the specific adulterant. However, with the developmentof multiple adulterants, each of which is chemically distinct and eachof which is capable of destroying or masking drugs of abuse or theirmetabolites, the process of identifying adulterated urine samplesbecomes increasingly difficult. Multiple tests must be performed on eachsample to assure detection of all chemically adulterated samples.Furthermore, there is a period of time for each adulterant during whichsamples containing that adulterant are not detected because thetest-specific adulterant has not yet been identified and/or confirmed.

Sample adulteration can affect many of the commonly used methods fordetection of drugs of abuse including, for example, enzyme immunoassay(EMIT or EIA), radioimmunoassay (RIA), and florescent polarizationimmunoassay (FPIA) and so forth. Consequently, clinical chemistryliterature recommends, and SAMSHA Mandatory Guidelines for FederalWorkplace Drug Testing Programs now require, that testing for drugs ofabuse in urine samples include testing for adulterants to identify urinesamples that have been adulterated.

Various compositions and methods have been developed to detect one ormore of a group of adulterants that are added to biological samples suchas urine to prevent detection of drugs of abuse. Examples of suchcompositions include chromophoric agents such as, for example,3,3′,5,5′-tetramethylbenzidine, diaminobenzidine,3-amino-9-ethylcarbazone, 4-chloro-1-napthol,2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid,ortho-phenylene-diamine, and so forth.

There is a need for enhancing detection of adulterants in samples foranalysis of drugs of abuse. In particular, there is a need forincreasing sensitivity of compositions used for detection ofadulterants. The enhanced detection of adulterants should be realizedfor both manual and automatic processes.

SUMMARY OF EMBODIMENTS OF THE INVENTION

In some embodiments, the present methods are employed for detecting anadulterant in a biological sample. A combination of a biological sample,an agent for detecting the adulterant and an ionic moiety capable ofundergoing reduction by gaining electrons is provided in an assaymedium. The combination is incubated under conditions sufficient for theionic moiety to undergo reduction and for the agent for detecting theadulterant to interact with the adulterant. The reduction of the ionicmoiety enhances the detection of the adulterant as a result ofincreasing the sensitivity of the agent for detecting the adulterant.The extent of interaction between the agent for detecting the adulterantand the adulterant is measured. The extent of the interaction is relatedto the presence or absence of the adulterant in the biological sample.

In some embodiments of the methods for detecting an oxidant adulterantin a biological sample, a combination of a biological sample, achromogenic compound and a source of ferric ions is provided in an assaymedium. The combination is incubated under conditions sufficient for theferric ions to undergo reduction to ferrous ions and for the chromogeniccompound to interact with the oxidant adulterant. The extent ofinteraction between the chromogenic compound and the oxidant adulterantis determined and the extent thereof is related to the presence orabsence of the oxidant adulterant in the biological sample.

Some embodiments of the present invention are directed to a test devicecomprising a support that comprises one of both of an agent fordetecting an adulterant in a biological sample and a source of metalions.

In some embodiments the present invention is directed to kits comprisingin packaged combination an agent for detecting an adulterant in abiological sample and a source of metal ions.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to better illustrate the embodimentsof the apparatus and technique of the present invention. The figures arenot to scale and some features may be exaggerated for the purpose ofillustrating certain aspects or embodiments of the present invention.

FIG. 1 is a schematic depicting an embodiment of a device in accordancewith embodiments of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Before the subject invention is described further, it is to beunderstood that the invention is not limited to the particularembodiments of the invention described below, as variations of theparticular embodiments may be made and still fall within the scope ofthe appended claims. It is also to be understood that the terminologyemployed is for the purpose of describing particular embodiments, and isnot intended to be limiting. Instead, the scope of the present inventionwill be established by the appended claims.

In this specification and the appended claims, the singular forms “a,”“an” and “the” include plural reference unless the context clearlydictates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood to one of ordinary skill in the art to which this inventionbelongs.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range, and any other stated or intervening value in thatstated range, is encompassed within the invention. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges, and are also encompassed within the invention, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the invention.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which this invention belongs. Although any methods, devicesand materials similar or equivalent to those described herein can beused in the practice or testing of the invention, the preferred methods,devices and materials are now described.

Embodiments of the present methods are employed in conjunction with theexamination of biological samples for the presence of one or more drugsof abuse where there is an interest in determining whether thebiological sample has been adulterated. An ionic moiety that is capableof undergoing reduction is used to increase the sensitivity of an agentfor detecting the presence of an adulterant in the biological sample.

The terms “drugs of abuse” or “analyte” includes the drugs themselvesand their metabolites and the like and may include therapeutic drugsthat are otherwise legal but are misused. The drugs of abuse aregenerally from about 100 to about 2,000 molecular weight, or from about125 to about 1,000 molecular weight. Representative drugs of abuse(including misused drugs), by way of example and not limitation, include(i) alkaloids such as morphine alkaloids, which include morphine,codeine, heroin, dextromethorphan, their derivatives and metabolites;cocaine alkaloids, which include cocaine and benzyl ecgonine, theirderivatives and metabolites; ergot alkaloids, which include thediethylamide of lysergic acid; steroid alkaloids; iminazoyl alkaloids;quinazoline alkaloids; isoquinoline alkaloids; quinoline alkaloids,which include quinine and quinidine; diterpene alkaloids, theirderivatives and metabolites; (ii) steroids, which include the estrogens,androgens, and reocortical steroids, bile acids, cardiotonic glycosidesand aglycones, which includes digoxin and digoxigenin, saponins andsapogenins, their derivatives and metabolites; steroid mimeticsubstances, such as diethylstilbestrol; (iii) lactams having from 5 to 6annular members, which include the barbiturates, e.g., Phenobarbital andsecobarbital, diphenylhydantoin, primidone, ethosuximide, and theirmetabolites; (iv) aminoalkylbenzenes, with alkyl of from 2 to 3 carbonatoms, which include the amphetamines; catecholamines, which includeephedrine, L-dopa, epinephrine; narceine; papaverine; and metabolites ofthe above; (v) benzheterocyclics which include oxazepam, chlorpromazine,tegretol, their derivatives and metabolites, the heterocyclic ringsbeing azepines, diazepines and phenothiazines; (vi) purines, whichincludes theophylline, caffeine, their metabolites and derivatives;(vii) drugs derived from marijuana, which include cannabinol andtetrahydrocannabinol; (viii) hormones such as thyroxine, cortisol,triiodothyronine, testosterone, estradiol, estrone, progesterone, (ix)tricyclic antidepressants, which include imipramine,dismethylimipramine, amitriptyline, nortriptyline, protriptyline,trimipramine, chlomipramine, doxepine, and desmethyldoxepin; and (x)anti-neoplastics, which include methotrexate; and the like.

The analyte may be a molecule found directly in a sample such asbiological sample, which term includes body fluids or tissue from ahost. The sample can be examined directly or may be pretreated to renderthe analyte more readily detectable by removing unwanted materials. Thesample may be pretreated to separate or lyse cells; precipitate,hydrolyse or denature proteins; hydrolyze lipids; solubilize theanalyte; or the like. Such pretreatment may include, without limitation:centrifugation; treatment of the sample with an organic solvent, forexample, an alcohol, such as methanol; and treatment with detergents.The sample can be prepared in any convenient medium, which does notinterfere with an assay. An, aqueous medium is preferred.

The phrase “biological sample” refers to any biological material suchas, for example, body fluid, tissue and the like, which is obtained fromthe body of a mammal and which is suspected of containing one or moredrugs of abuse. Body fluids include, for example, whole-blood, plasma,serum, interstitial fluid, sweat, saliva, urine, semen, blister fluid,inflammatory exudates, stool, sputum, cerebral spinal fluid, tears,mucus, lymphatic fluid, vaginal mucus, and the like. The biologicaltissue includes excised tissue from an organ or other body part of ahost, e.g., tissue biopsies; hair and skin; and so forth.

The adulterants mentioned above include any substance (or combinationthereof) that may be added to the biological sample to be tested eitherby direct addition or by indirect addition such as by ingestion and thelike. The substance is added to the biological sample to adverselyaffect a screening assay or a confirmation process. Such substancesinclude many household products and also commercially available productssold for the purpose of obscuring the result of a drug test. Thesubstance may be an oxidation-based adulterant or oxidant such as, forexample, a nitrite such as, e.g., sodium nitrite, etc., a bromate suchas, e.g., sodium bromate, potassium bromate, etc., bromine, bleach(sodium hypochlorite), a chromate such as, e.g., pyridiniumchlorochromate (chromium VI), etc., a peroxide, e.g., hydrogen peroxide,etc., either alone or in conjunction with a peroxidase enzyme, an iodinecontaining compound such as, for example, iodine, iodate, e.g., sodiumiodate, etc., iodic acid, periodate, e.g., sodium periodate, etc., andthe like. Many of the above substances are relatively strong oxidizingagents and are the active ingredient in many commercial productsspecifically sold for the purpose of adulterating biological samples.

Other adulterants to which the present methods may find application,other than a general oxidant test, include, for example, enhancement ofa test for a specific oxidant such as, e.g., bleach or nitrite, and thelike.

The amount of adulterant that may be in a biological sample is usuallythat which is added by an external source either directly or indirectlyas discussed above. The amount of adulterant is dependent on the natureof the adulterant, the nature of the biological sample, the nature ofthe assay being used to detect the drug of abuse, and so forth. Theamount of adulterant added is usually at least that which is sufficientto render an assay for a drug of abuse ineffective in detecting the drugof abuse and may be greater but not so great as to render the adulterantreadily detectable by visual or other inspection. In general, the amountof adulterant in the biological sample can vary wildly depending on howmuch an individual adds to the sample; but, in general, such individualwould only want to add enough adulterant to render the initial screennegative and not enough to change the physical appearance or odor of thesample. Obviously, the amount of adulterant in the assay medium isdependent on the amount in the biological sample, which may be dilutedby additional components of the assay medium.

Various agents for detecting adulterants have been developed. Suchagents include, for example, chromogenic compounds, and the like, whichare most easily subject to automation. Detection may also occur bymeasurement of physical properties such as, for example, pH, specificgravity, and the like.

As mentioned above, one group of agents for detecting adulterantsincludes chromogenic compounds that are capable of being oxidized by theadulterant to produce a product detectable by visual or otherinspection, usually, a colored product. The phrase “capable of being”means that the particular substance will undergo the recited operationif the conditions for the operation are present. For example, capable ofbeing oxidized means that the substance will undergo oxidation to adetectable level when the adulterant is present. Examples of chromogeniccompounds include, by way of illustration and not limitation,2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS);3-amino-9-ethylcarbazone; naphthols such as, for example,4-chloro-1-napthol, and the like; phenylamine chromogenic indicatorssuch as, for example, N,N,N,N-tetramethyl-1,4-phenylenediamine,N,N-diethyl-1,4,-phenylenediamine,2,3,5,6-tetramethyl-1,4-phenylenediamine,N,N-dimethyl-p-phenylenediamine, 2,4,6-trimethyl-1,3-phenylenediamine,N,N,N,N-tetramethylbenzidine, 3,3,5,5-tetramethylbenzidine,N,N,N,N-tetramethyl4,4-diaminestilbene, diamine-benzidine,ortho-phenylenediamine, and 0-toluidine, and so forth. Particularexamples of chromogenic compositions for detecting adulterants may befound in U.S. Pat. No. 6,503,726 (Anne, et al.), and U.S. PatentPublication No. 20030138959 (Carter, et al.), the disclosures of whichare incorporated herein by reference.

The amount of agent for detecting an adulterant is that which issufficient to render an assay for the adulterant effective in, orsufficient for, detecting the adulterant and is dependent on the natureof the agent, the nature of the adulterant, the nature of the biologicalsample, composition of the sample as a result of the health of theindividual and any medications or vitamins they may ingest, and soforth. In general, the amount of agent for detecting an adulterant inthe assay medium is variable depending on the redox potential of theagent itself. In many instances the amount of agent employed fordetecting an adulterant is specified by the manufacturer of the productcomprising the agent.

As mentioned above, in accordance with embodiments of the presentinvention, an ionic moiety capable of undergoing reduction by gainingelectrons is included in a medium comprising the biological sample andthe agent for detecting the adulterant. The nature of the ionic moietyis related to the nature of the agent for detecting the adulterant. Theionic moiety must not deleteriously affect to any significant extent theactivity of the agent for detecting the adulterant. The ionic moiety isparticularly effective in enhancing the sensitivity of agents fordetecting oxidation-based adulterants. In some embodiments the ionicmoiety is a metal ion of a metal such as, for example, a Group VIIImetal, a Group VIIB metal, a Group IB metal, and the like. For example,metals include iron, silver, copper, manganese, nickel, platinum, and soforth. Examples of suitable metal ions include ferric, silver (+1),cupric, manganese (+4), nickel (+2 and +4)), platinum (+4), and thelike. For example, ferric ion is capable of gaining electrons to go fromthe Fe⁺³ state to the Fe⁺² state.

The metal ion is usually present with a co-ion, which should not affectto any significant extent the activity of the agent for detecting theadulterant. The co-ion should not itself be an adulterant. Examples ofsuitable co-ions include, for example, chloride, sulfate, bromide,fluoride, iodide, oxide, and the like. The ionic moiety and its co-ionmay be present in the dry state or in solution, usually in an aqueousmedium. If present in solution, the amount of the ionic moiety issufficient such that when the solution is added to an assay medium orbecomes an assay medium, the ionic moiety is present in the desiredamount or concentration in accordance with embodiments of the presentinvention.

The amount of ionic moiety is that which is sufficient to enhance thesensitivity of the agent for detecting the adulterant and is dependenton the nature of the agent, the nature of the adulterant, the nature ofthe biological sample, and so forth. The amount of the ionic moiety isusually determined on an empirical basis. In general, the amount ofionic moiety in the assay medium is small compared to the concentrationof the chromogenic portion of the assay. As an example using ferric ionfor purposes of illustration and not limitation, in many embodiments theconcentration of the ferric ion in the resultant assay medium (i.e.,after addition of ferric ion as a solid or liquid reagent) is about 0.1to about 100 μg/mL, about 0.5 to about 50 μg/mL, about 1 to about 30μg/mL, about 2 to about 10 μg/mL, and so forth.

In some embodiments the ionic moiety is provided as a separate reagenteither in a suitable liquid medium or in the dry state. Various buffersmay be employed to assist in maintaining a pH to enhance solubility ofthe ionic moiety in an aqueous medium, which may be similar to theaqueous media discussed above for the assay medium. The nature of thebuffer will depend on the nature of the ionic moiety including itssolubility requirements. Other materials may also be present with theionic moiety such as stain preventing materials and the like. Forexample, sodium dodecyl sulfate may be employed at a concentration thatreduces or eliminates staining of assay reaction vessels so that thevessels may be reused after suitable washing.

The examination of the biological sample for the presence of theadulterant is usually carried out in an assay medium, which may be amedium that is the same as, or different from, the medium for conductingan assay for the detection of the drug of abuse. In some embodiments thebiological sample provides the assay medium, which is contacted with anassay medium comprising the agent for detecting an adulterant, an ionicmoiety, buffers and the like are added. Various buffers may be added tothe biological sample to adjust pH and the like. In some embodiments theassay medium is an aqueous buffered medium to which the biologicalsample and other agents are added. The pH of the assay medium is low tomoderate, generally that which provides optimum assay sensitivity. Theaqueous medium may be solely water or may include from 0.1 to about 40volume percent of a cosolvent such as, for example, an organic solvent,e.g., an alcohol, an ether, and the like. The pH for the medium willusually be in the range of about 2 to about 11, about 4 to about 11,more usually in the range of about 5 to about 10, and preferably in therange of about 6.5 to about 9.5. The pH will usually be a compromisebetween that which is optimum for bringing about interaction between theagent for detecting the adulterant and the adulterant and the reductionof the ionic moiety, and so forth.

Various buffers may be used to achieve the desired pH and maintain thepH during the determination. Illustrative buffers include borate,phosphate, carbonate, tris, barbital and the like. The particular bufferemployed is not critical to this invention, but in an individual assayone or another buffer may be preferred. Various ancillary materials maybe employed in the above methods. For example, in addition to buffersthe medium may comprise stabilizers for the medium and for the reagentsemployed. Frequently, in addition to these additives, proteins may beincluded, such as albumins; organic solvents such as formamide;quaternary ammonium salts; polyanions such as dextran sulfate;surfactants, particularly non-ionic surfactants; binding enhancers,e.g., polyalkylene glycols; or the like.

As mentioned above, a combination of the biological sample, which issuspected of containing an adulterant, an agent for detecting anadulterant, and the ionic moiety is formed in an assay medium. While theorder of addition may be varied widely, there will be certainpreferences depending on the nature of the assay. The simplest order ofaddition is to add all the materials simultaneously and examine themedium for the presence of a signal indicating the presence of theadulterant in the biological sample. Alternatively, the reagents can becombined sequentially. Optionally, an incubation step may be involvedsubsequent to each addition as discussed above.

The combination is incubated under conditions sufficient for the ionicmoiety to undergo reduction and for the agent for detecting theadulterant to interact with the adulterant. One or more incubationperiods may be applied to the medium at one or more intervals includingany intervals between addition of various reagents mentioned above. Themedium is usually incubated at a temperature and for a time sufficientfor the various interactions to occur. Moderate temperatures arenormally employed for carrying out the method and usually constanttemperature, preferably, room temperature, during the period of themeasurement. Incubation temperatures range from about 5° to about 99°C., from about 15° C. to about 70° C., from about 20° C. to about 45° C.The time period for the incubation is about 0.2 seconds to about 6hours, about 2 seconds to about 1 hour, about 1 to about 5 minutes. Thetime period depends on the temperature of the medium the rate of thevarious interactions, and so forth. Temperatures during measurementswill generally range from about 10 to about 50° C., from about 15 toabout 40° C.

The nature of the signal that is observed is dependent on the nature ofthe agent for detecting an adulterant. For chromogenic compositions, thesignal is usually a color that is detectable either visually orinstrumentally or both. For example, clinical instruments that areemployed currently to measure color formation in assays conducted inclinical laboratories may be employed. The level of the signal detectedis related to the presence of the adulterant in the biological sample.In general, a predetermined cut-off level is established for theadulterant. The particular predetermined cut-off level generally isdetermined on an adulterant-by-adulterant basis. Those skilled in theart are well aware of the factors relating to the selection ofpredetermined cut-off levels. Usually, the predetermined cut-off levelis dependent on the smallest amount of adulterant that is necessary torender the assay for a drug of abuse ineffective.

The format for conducting the determination of an adulterant inaccordance with embodiments of the present methods is dependent on thenature of the adulterant, the nature of the agent for detecting theadulterant, the nature of the ionic moiety, the nature of the sample,and so forth. The assay may be carried out in a reaction vessel such as,for example, a well of a microtiter plate, a cuvette, test tube, anautomated instrument which can process sample, and the like. In someembodiments the reagents may simply be added to the reaction vesselalong with the biological sample and the medium is then examined for thepresence and/or amount of a signal. In some embodiments one or more ofthe reagents may be present on a support such as, for example, a porousmember, which may be contacted with the assay medium or on which theassay is carried out. One or more of the reagents may be attached to asupport diffusively such as, for example, by impregnation, drying,adsorption, and the like, or non-diffusively such as, for example, bycovalent binding and the like.

In some embodiments one or more of the reagents may be present on aporous member usually in a diffusive manner so that the reagents maydissolve in the assay medium. In some circumstances one or more of thereagents may be present on the porous member in a non-diffusive manner.The present embodiments have application to all assay formats fordetecting adulterants in biological samples.

In some embodiments the porous member comprises a porous material havingpores of at least 0.1 microns, at least 1.0 micron, may be employed. Theporous material can be attached to a support. On the other hand, theporous material may provide its own support. The porous material may befunctionalized to permit bonding of one or more reagents for performingembodiments of the present methods. On the other hand, the porousmaterial may be of such composition that one or more reagents are boundin a non-covalent manner by adsorbtion, impregnation, and the like.

For example, in some embodiments impregnation is employed, which can becarried out in one or more impregnation steps. Each impregnation maycontain one or more of the chemical compounds making up the assayreagent composition; the exact procedure is dictated by theinter-reactivity of the assay constituents and the order in which theymay have to react with each other or the adulterant depending on theparticular protocol and reagents employed. The impregnation may becarried out with solutions of the required reagents in volatilesolvents, such as water, methanol, ethanol or acetone. This may beaccomplished in one impregnating step. Frequently however, it isadvisable to carry out the impregnation in several steps where multiplesolutions are used, which in each case contain one or more of thereagents.

The porous materials are generally hydrophilic or are capable of beingrendered hydrophilic and preferably are cellulosic materials andmaterials derived from cellulose, such as fiber containing papers, e.g.,filter paper, chromatographic paper, etc., but may include inorganicpowders such as silica, magnesium sulfate, and alumina; and othernatural polymeric materials, and synthetic or modified naturallyoccurring polymers, such as nitrocellulose, cellulose acetate, poly(vinyl chloride), polyacrylamide, cross linked dextran, agarose,polyacrylate, etc.; either used by themselves or in conjunction withother materials; ceramic materials; and the like.

The piece of porous member can be a single structure such as a sheet cutinto strips or pads or it can be several strips or pads or particulatematerial. The porous member can have a rectangular, circular, oval,triagonal or other shape. The porous member in a desired form may bebound to a support or solid surface such as found, for example, inthin-layer chromatography and may have an absorbent pad either as anintegral part or in liquid contact. The porous member can be comprisedof several segments in liquid receiving relationship and preferablybound to a support. The porous member can also be a sheet having lanesthereon or capable of spotting to induce lane formulation, wherein aseparate assay can be conducted in each lane.

The support for one of more of the reagents above or for the porousmember, where a support is desired or necessary, will normally be waterinsoluble, non-porous, and rigid and usually will be of the same lengthand width as the bibulous member but may be larger or smaller. A widevariety of organic and inorganic materials, both natural and synthetic,and combinations thereof, may be employed provided only that the supportdoes not interfere with the function of the porous member or thereagents for the assay. Illustrative polymers include polyethylene,polypropylene, poly(4-methylbutene), polystyrene, polymethacrylate,poly(ethylene terephthalate), nylon, poly(vinyl butyrate), poly (vinylchloride), polyacrylamide, polyacrylate, and the like, either used bythemselves or in conjunction with other materials. Other supportmaterials include, for example, glass, ceramics, metals, and the like.The support can have any one of a number of shapes, such as strip, rod,plate, well, particle, bead or the like.

The porous member may be partially or substantially completely enclosedin a protective casing, conveniently a clear or partially, or in somesituations completely, opaque enclosure. Depending upon the particularprotocols involved and the construction of the device, the enclosure maybe removable or irremovable, may encase only the porous member or mayencase additionally all or a portion of a support. The enclosure mayprovide for one or more windows and will normally be of a sturdy inertimpermeable material that will provide mechanical protection for theporous member and will not interfere with the performance of the assay.Normally an air opening will be provided to prevent the entrapment ofair within the enclosure.

In a strip format where an assay medium traverses at least a portion ofthe porous member, the porous member may have a length of about 1.5 toabout 30 cm, about 2 to about 20 cm. The width may vary from about 0.1mm to about 3 cm. The thickness will generally be about 0.1 mm to about5 mm, from about 0.5 to about 3 mm. In a pad format, the porous memberwill generally have a thickness of about 0.5 to about 10 mm and an areaof about 25 to about 150 square millimeters (mm²).

Exemplary formats as are known in the art are discussed below by way ofillustration and not limitation. In one format, the agent for detectingthe adulterant is impregnated in a pad to provide a test stripimmunoassay. In accordance with embodiments of the peasant invention, anionic moiety is either also impregnated in the pad or added to an assaymedium comprising the biological sample, which is contacted with thepad.

In another exemplary format, a device using assay strips is employedwhere two sets of parallel strips are mounted back-to-back. Each set ofstrips is visible through a window on the front or back faces of thedevice. The assay medium comprising the biological sample is contactedwith the device through an aperture in the device enclosure and carriedto the test strips by a wick in the form of a piece of blotting paper.Contact of the assay medium may be carried out by means of a pipette orthe bottom portion of the device can be dipped in a container comprisingthe assay medium. One of the test strips visible through a separatewindow is used to detect an adulterant in the biological sample and,accordingly, comprises an agent for detecting the adulterant. An ionicmoiety in accordance with embodiments of the present invention ispresent on the test strip or in the assay medium.

Other exemplary formats involve test strips in the form of dry chemistrydipsticks, or on-site test modules utilizing thin layer chromatographyin a lateral flow format, or other similar technology. Afterimpregnation, the dipsticks are dried, cut into strips, glued to asupport as part of a “sandwich” composed of a handle, test pad. Aportion of or the entire dipstick may be enclosed in a synthetic resinfilm and/or a fine-mesh material and/or water stable film as known inthe art.

An embodiment of a test device is shown in FIG. 1. Test device 10comprises porous pad 12 affixed to a plastic strip 14. Pad 12 isimpregnated with an agent for detecting an adulterant 16 and with anionic moiety 18.

Kits

Another aspect of the present invention relates to kits useful forconveniently performing an assay for the determination of an adulterantin a biological sample. In some embodiments the kits comprise inpackaged combination an agent for detecting an adulterant in abiological sample and a source of metal ions. In some embodiments thekits comprise a test device 10 as described above and one or morebuffers for addition to an assay medium. In some embodiments the kitscomprise a test device comprising an agent for detecting an adulterantand separately packaged ionic moiety reagent as well as one or morebuffers, one or more bulk reagents for an automated device, and soforth. In some embodiments the kits comprise a test device thatcomprises a strip, plate, well.

To enhance the versatility of the subject invention, the kit reagentscan be provided in packaged combination, in the same or separatecontainers, in liquid or lyophilized form so that the ratio of thereagents provides for substantial optimization of the method and assay.The reagents may each be in separate containers or various reagents canbe combined in one or more containers depending on the cross-reactivityand stability of the reagents. Furthermore, one or more of the abovereagents may be present on a porous member of a device. The kit canfurther include other separately packaged reagents for conducting anassay such as additional binding members, ancillary reagents suchbuffers, and so forth. The relative amounts of the various reagents inthe kits can be varied widely to provide for concentrations of thereagents that substantially optimize the reactions that need to occurduring the present method and further to optimize substantially thesensitivity of the assay. Under appropriate circumstances one or more ofthe reagents in the kit can be provided as a dry powder, usuallylyophilized, including excipients, which on dissolution will provide fora reagent solution having the appropriate concentrations for performinga method or assay in accordance with the present invention. The kit canfurther include a written description of a method in accordance with thepresent invention as described above.

USE OF EMBODIMENTS

Embodiments of the present invention may be utilized in conjunction withmany known assay for drugs of abuse. The assay methods usually involve abiological sample, which is combined in an assay medium with reagentsfor carrying out the assay. Such reagents may include a binding partnerfor the analyte such as, e.g., an antibody for the analyte, analyteanalogs, solid surfaces to which one of the above reagents is bound,binding partners for binding partners, and so forth. One or more of thereagents can be labeled with a label such as, e.g., an enzyme. Thereagents are chosen such that a signal is obtained from a label inrelation to the presence or amount of analyte in the sample.

The assays can be performed either without separation (homogeneous) orwith separation (heterogeneous) of any of the assay components orproducts. Homogeneous immunoassays are exemplified by the EMIT® assay(Dade Behring Inc.) disclosed in Rubenstein, et al., U.S. Pat. No.3,817,837; immunofluorescence methods such as those disclosed in Ullman,et al., U.S. Pat. No. 3,996,345, column 17, line 59, to column 23, line25; enzyme channeling immunoassays (“ECIA”) such as those disclosed inMaggio, et al., U.S. Pat. No. 4,233,402, column 6, line 25 to column 9,line 63; the fluorescence polarization immunoassay (“FPIA”) asdisclosed, for example, in, among others, U.S. Pat. No. 5,354,693; andso forth.

Other enzyme immunoassays are the enzyme modulate mediated immunoassay(“EMMIA”) discussed by Ngo and Lenhoff, FEBS Left. (1980) 116:285-288;the substrate labeled fluorescence immunoassay (“SLFIA”) disclosed byOellerich, J. Clin. Chem. Clin. Biochem. (1984) 22:895-904; the combinedenzyme donor immunoassays (“CEDIA”) disclosed by Khanna, et al., Clin.Chem. Acta (1989) 185:231-240; homogeneous particle labeled immunoassayssuch as particle enhanced turbidimetric inhibition immunoassays(“PETINIA”), particle enhanced turbidimetric immunoassay (“PETIA”),etc.; and the like.

Exemplary of heterogeneous assays are the enzyme linked immunosorbantassay (“ELISA”) discussed in Maggio, E. T. supra; the radioimmunoassay,disclosed in Yalow, et al., J. Clin. Invest. 39:1157 (1960) and soforth.

Embodiments of the present invention may also be utilized in conjunctionwith multi-analyte immunoassays where one or more drugs of abuse. Suchmulti-analyte systems are described, for example, in Loor, et al., J.Anal. Toxicol. 12: 299 (1988).

As mentioned above, after an initial screening assay is performed,biological samples yielding positive results are subjected to aconfirmation, assay, such as, for example, GC-MS to verify the resultsof a positive screen for drugs of abuse. The GC-MS analysis costs manytimes more than an initial screen. Every additional unnecessary GC-MSperformed drives up the overall cost of drug testing. Eliminating theseadditional, unnecessary assays saves millions of dollars per year. As aresult of conducting an assay for an adulterant in accordance withembodiments of the present invention, unnecessary time and reagents maybe s saved. Tests may be halted as soon as the presence of theadulterant is detected. The ability to terminate the screening processby ascertaining the presence of an adulterant results in reducedtechnician's efforts and time, providing an economic savings to thetesting laboratory. Furthermore, the early interruption and cessation ofthe automated screening process may facilitate earlier recovery of asubstitute biological sample from the person being tested, providingmore accurate determinations to the requestor of the testing.

Furthermore, false positive drug screens strongly impact on-sitetesting. In most situations utilizing on-site tests (on site devicessuch as dipstick or lateral flow devices require no instrumentation,making these devices ideal for collection and on site facilities) theemployee is screened upon arrival for work. If a positive is obtainedusing the on-site test, a second sample is forwarded to the lab forGC-MS confirmation and the employee is suspended from work or reassignedto other duties until the results of the test are known. Therefore, itis of vital importance that the employer and laboratory know if thesample has had an adulterant added to save time, money, and so forth.

The invention is demonstrated further by the following illustrativeexamples.

EXAMPLES

Parts and percentages herein are by weight unless otherwise indicated.Temperatures are in degrees Centigrade (OC). All materials were fromSigma-Aldrich, Saint Louis Mo. unless indicated otherwise.

Materials: Reagent 1 (agent for detection of an adulterant) contained0.42 g/L of 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt in 50 mM Glycine-HCl at pH 2.1 with 0.01% sodium dodecylsulfate (SDS). Reagent 2 (in accordance with some embodiments of theinvention) contained 12.2 μg/mL of ferric chloride in 50 mM Glycine-HClat pH 2.1 with 0.01% SDS. 247 μL of Reagent 1 was mixed with 103 μL ofReagent 2 and 5 μL of sample, which was prepared at the appropriate testconcentrations as set forth in the table below. The mixture wasincubated at 37° C. for 13 minutes and the absorbance was measured at700 nm using a HITACHI 717 (Roche-Hitachi, Indianapolis Ind.).

The OX PERFECT® reagent used for comparison was a commercial reagentsold by Dade Behring Inc., Newark Del. The parameters andrecommendations in the package insert for using the reagent werefollowed.

The adulterants were all prepared as stocks in aqueous medium. PCC ispyridinium chlorochromate. Both methods were calibrated with 2.5 mg/dLof sodium dichromate. The detection limit was defined as the thresholdbelow which the test substance produced an absorbance less than theabsorbance of 2.5 mg/dL of solution of sodium dichromate.

Testing was done using the HITACHI 717. The results are summarized inTable 1.

TABLE 1 Detection Limit (mg/dL) Detection Limit (mg/dL) Adulterant withoX Perfect kit with ferric ion Iodate 130 60 Iodic acid 50 55 Iodine 2018 Periodate 15 8 Dichromate 2.5 2.5 Peroxide 10 4 Bleach 4 4 PCC 5 5Nitrite 1 1

The results show that the use of ferric ion enhanced the detection limitof the adulterant. It should be noted that the results for OX PERFECTreagent are the best results obtained from multiple runs and differentreagent lots. Accordingly, for some adulterants an enhancement indetection limit was not seen over the commercial reagent at theconcentration of ferric ion used.

All publications and patent applications cited in this specification areherein incorporated by reference as if each individual publication orpatent application were specifically and individually indicated to beincorporated by reference.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it will be readily apparent to those of ordinary skill inthe art in light of the teachings of this invention that certain changesand modifications may be made thereto without departing from the spiritor scope of the appended claims. Furthermore, the foregoing description,for purposes of explanation, used specific nomenclature to provide athorough understanding of the invention. However, it will be apparent toone skilled in the art that the specific details are not required inorder to practice the invention. Thus, the foregoing descriptions ofspecific embodiments of the present invention are presented for purposesof illustration and description; they are not intended to be exhaustiveor to limit the invention to the precise forms disclosed. Manymodifications and variations are possible in view of the aboveteachings. The embodiments were chosen and described in order to explainthe principles of the invention and its practical applications and tothereby enable others skilled in the art to utilize the invention.

1. A method for detecting an adulterant in a biological sample, saidmethod comprising: (a) providing in combination in a reaction medium abiological sample, an agent for detecting the adulterant and a metal ioncapable of undergoing reduction by gaining electrons, (b) incubating thecombination under conditions sufficient for the metal ion to undergoreduction and for the agent for detecting the adulterant to react withthe adulterant, and (c) determining the extent of reaction between theagent for detecting the adulterant and the adulterant wherein the extentthereof is related to the presence or absence of the adulterant in thebiological sample.
 2. A method according to claim 1 wherein theadulterant is an oxidant.
 3. A method according to claim 1 wherein theagent for detecting the adulterant is a chromogenic compound.
 4. Amethod according to claim 3 wherein the chromogenic compound is selectedfrom the group consisting of2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid,3,3′,5,5′-tetramethylbenzidine, diaminobenzidine,3-amino-9-ethylcarbazone, 4-chloro-1-napthol, andortho-phenylene-diamine.
 5. A method according to claim 1 wherein themetal ion is of a metal from Group VIII, Group VIIB or Group IB.
 6. Amethod according to claim 5 wherein the metal ion is of a metal selectedfrom the group consisting of iron, silver, copper, manganese, nickel,and platinum.
 7. A method according to claim 1 wherein the adulterant isselected from the group consisting of peroxide, iodate, periodate,chromate, nitrite, iodine, iodic acid and bleach.
 8. A method accordingto claim 1 wherein the biological sample is urine.
 9. A method accordingto claim 1 wherein the determining involves a test device comprising theagent for detecting the adulterant.
 10. A method according to claim 9wherein the test device comprises a strip, plate, well, cuvette, testtube or automatic device for processing clinical samples.
 11. A methodfor detecting an oxidant adulterant in a biological sample, said methodcomprising: (a) providing in combination in a reaction medium abiological sample, a chromogenic compound and a source of ferric ions,(b) incubating the combination under conditions sufficient for theferric ions to undergo reduction to ferrous ions and for chromogeniccompound to react with the oxidant adulterant, and (c) determining theextent of reaction between the chromogenic compound and the oxidantadulterant wherein the extent thereof is related to the presence orabsence of the oxidant adulterant in the biological sample.
 12. A methodaccording to claim 11 wherein the chromogenic compound is a substratefor a peroxidase.
 13. A method according to claim 11 wherein thechromogenic compound is selected from the group consisting of2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid,3,3′,5,5′-tetramethylbenzidine, diaminobenzidine,3-amino-9-ethylcarbazone, 4-chloro-1-napthol, ortho-phenylene-diamine.14. A method according to claim 11 wherein the oxidant adulterant isselected from the group consisting of peroxide, iodate, periodate,chromate, nitrite, iodine, iodic acid, and bleach.
 15. A methodaccording to claim 11 wherein the biological sample is urine.